Contact lens holder

ABSTRACT

A lens holder is disclosed that includes a base having first and second corresponding convex surfaces on opposite sides with a pivot axis on the base adjacent the surfaces. First and second cover members of identical construction cooperate with opposite sides of the base and are pivoted on the pivot axis. The identical cover members each include a concave surface corresponding in configuration to the convex surfaces on the base and a pair of arms on one end of each cover member that define pivot surfaces. The pivot surfaces receive the pivot axis and the arms are positioned so that the first and second cover members have lateral edges aligned with each other, when the arms of the cover members are operatively engaged with the pivot axis. The cover members each include latch means releasably retaining the cover member in a closed position on the base in which the convex and concave surfaces are in juxtaposed relation to each other. The base is removably secured to a cap and the cap is adapted to be removably coupled to a container with the cap, base and cover positioned to locate the base in the container when the cap is coupled to the container. In addition, the cap defines a maximum pivoted position for the cover members when it is secured to the container to prevent separation of the cover members from the base, while the cover members can readily be separated from the base when the base is removed from the cap.

United States Patent 1191 Thomas 1 1 Nov. 6, 1973 CONTACT LENS HOLDER[75] Inventor: Michael D. Thomas, Elmhurst, Ill.

[73] Assignee: MCD Corporation, Bensenville, Ill.

[22] Filed: Mar. 3, 1972 [2]] Appl. No.: 231,665

[52] U.S. Cl. 206/5 A, 134/143 [51] Int. Cl. A45c 11/00, B08b ll/OO [58]Field of Search ..134/117,135,137,

[56] References Cited UNITED STATES PATENTS 2,609,828 9 1952 Ward 134166 R x 2,839,217 6/1958 Trudeau.. 220/32 2,932,383 4 1960 Fagan 206 5 A3,115,146 12/1963 Erwin 206 5 A x 3,314,533 4/1967 Kopfle 206/5 A x3,444,868 5/1969 Hungerford et al. 134/143 3,545,458 12 1970 KOrd et al134 143 x 3,602,238 8/1971 Brown 1 134 117 3,661,248 5 1972 lSell et al.134 137 x Primary Examiner-Robert L. Bleutge Att0rneyMax Dressler et al.

[57] ABSTRACT A lens holder is disclosed that includes a base havingfirst and second corresponding convex surfaces on opposite sides with apivot axis on the base adjacent the surfaces. First and second covermembers of identical construction cooperate with opposite sides of thebase and are pivoted on the pivot axis. The identical cover members eachinclude a concave surface corresponding in configuration to the convexsurfaces on the base and a pair of arms on one end of each cover memberthat define pivot surfaces. The pivot surfaces receive the pivot axisand the arms are positioned so that the first and second cover membershave lateral edges aligned with each other, when the arms of the covermembers are operatively engaged with the pivot axis. The cover memberseach include latch means releasably retaining the cover member in aclosed position on the base in which the convex and concave surfaces arein juxtaposed relation to each other. The base is removably secured to acap and the cap is adapted to be removably coupled to a container withthe cap, base and cover positioned to locate the base in the containerwhen the cap is coupled to the container. In addition, the cap defines amaximum pivoted position for the cover members when it is secured to thecontainer to prevent separation of the cover members from the base,while the cover members can readily be separated from the base when thebase is removed from the cap.

14 Claims, 9 Drawing Figures PAT ENTEU NOV 6 i973 SHEET 10F 2 CONTACTLENS HOLDER BACKGROUND OF THE INVENTION The present invention relatesgenerally to holders for articles having a general shape of a section ofa sphere, and more particularly to an improved lens holder for a pair ofcontact lenses.

Corneal contact lenses constructed of a relatively hard plastic materialhave been known for years. Recently, corneal contact lenses have beendeveloped that are made of a soft, pliable plastic material. Some of therelatively soft, pliable plastic materials are quite hydrophilic innature. This means that the user of the lens must be extremely carefulto prevent contamination of the lens with materials that can be absorbedby the plastic. It also means that precautions must be taken to kill anybacteria or germs that may be absorbed by the lens during use which maycause inflammation or damage to the cornea of the user.

For these reasons, it is important to sterilize the corneal soft contactlenses daily. Sterilization of soft contact lenses requires that they beplaced in a saline solution and the solution heated sufficiently tocarry out the sterilization process. I

Normally this is accomplished by enclosing the soft contact lenses in acapsule that is partially filled with a saline solution and thensuspending the capsule in boiling water to heat the solution.

Numerous types of containers in which a pair of lenses are supported ina solution for sterilization and storage have been proposed. However,these are either extremely complicated in construction, which requireconsiderable attention of the user, or are unsatisfactory for propersterilization.

SUMMARY OF THE INVENTION The present invention provides a simple andinexpensive holder for a pair of contact lenses that can readily besuspended within a container for sterilization of the contact lenses,should they be of the soft, pliable plastic material that is hydrophilicin nature. The holder consists of a minimum number of plastic parts, twoof which are interchangeable so that a minimum number of dies need bemanufactured for producing the entire unit.

The holder is releasably secured in a cap that cooperates with acontainer to suspend the contact lenses in the container during thesterilization process and also allow the solution to come into contactwith both surfaces of the contact lenses.

The contact lens holder of the present invention includes a base havinga pair of opposed convex surfaces on opposite sides thereof and a pairof cover members, identical in construction, pivoted about a common axisdefined adjacent one end of the convex surfaces. The cover members eachhave a concave surface that corresponds to the configuration of theconvex surfaces on the base and also has a pair of arms extending fromone end, which arms define pivot surfaces to receive the pivot axis onthe base. The arms are positioned so that the first and second covermembers have lateral edges aligned with each other when the members areoperatively engaged with the pivot axis.

The cover members include latch means on the opposite ends thereof thathold the cover members in a closed position on the base with the convexand concave surfaces in juxtaposed relation to each other.

Each cover member also has a plurality of slots that extend from theconcave surface and terminate in an op posed surface to allow fluid toreadily come into contact with one surface of the contact lens supportedthereby, while the convex surfaces on the base have slits therein toallow the fluid to contact the opposite surface of the lens.

The base of the lens holder has a reduced extension at one end which isremovably secured to a cap that may be coupled to a container toposition the base within the container.

According to another aspect of the invention, the pivot surfaces arecylindrical in configuration and cir cumscribe an arc of less than sothat the cover members can be removed from the base after being pivotedto an extreme position on the pivot axis. However, when the base isassembled on the cap, the cap defines a maximum pivot position for therespective cover members, which is intermediate the extreme pivotedposition and the closed position to insure that the cover members remainon the base at all times.

As was indicated above, each cover member is identical in constructionto reduce the inventory required for forming the holders. This isaccomplished by having the pivot arms laterally offset or displaced toone side so that the center line between the arms of each pair does notcoincide with the center line of the cover. In addition, the latch meansconsists of a latch arm on the opposite end of the cover with the latcharm also laterally offset from the center line of the cover member.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF DRAWINGS FIG. 1 shows an explodedprespective view of the lens holder of this invention, for supporting apair of contact lenses;

FIG. 2 is an enlarged plan view of the base forming part of the holder;

FIG. 3 is a side elevation view of the base shown in FIG. 2;

FIG. 4 is a section view of the base, taken along line 44 of FIG. 2;

FIG. 5 is a plan view of one cover member forming part of the holder;

FIG. 6 is a side elevation of the cover member shown in FIG. 5;

FIG. 7 is a section of the cover member, taken generally along line 7-7of FIG. 5;

FIG. 8 is a plan view of the base and pair of cover members in closedcondition and assembled to the cap; and

FIG. 9 (appearing with FIG. 1) is a side elevation view of the base,cover member and cap with one of the cover members in an open positionand the other cover member shown partly in section.

DETAILED DESCRIPTION While this invention is susceptible of embodimentin many different forms, there is shown in the drawings and will hereinbe described in detail one specific embodiment, with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit theinvention to the embodiment illustrated.

FIG. 1 of the drawings shows the elements that comprise the lens holderof the present invention, including generally a base 12 and pair ofcover members 14, a cap 16, and a container 18.

The elements making up the lens holder are constructed to allow a pairof soft contact lenses to be supported in a fixed position upon the baseand the entire base suspended and sealed within the container so thatthe container can be utilized for sterilizing a pair of lenses as wellas storing them when they are not in use. Each of the elements will bedescribed separately and the relation of the elements will be outlinedin connection with assembly and use of the holder.

The base 12 (FIGS. 2-4) consists of a body 20 having convex surfaces 22on opposite sides located between lateral edges 24. The base has aplurality of slits 26 extending from each of the convex surfaces, for apurpose that will be described later.

The base 12 also has a reduced extension 30 at one end with lateraledges 32 of the extension being spaced inwardly from the lateral edges24 of the base. Each of the lateral edges of the extension 30 has anintegral pin extending outwardly therefrom, with the two pins 34defining a common pivot axis and terminating at the outer endsubstantially in alignment with the lateral edges 24 of the main body20. The pins 34 are positioned on the lateral edges to define gaps 36between the end surface 37 of the base 20 and the peripheral surface ofthe pins, for a purpose the will be described later. The opposite end ofthe base has a pair of cutouts 38 extending inwardly from the outerlateral edges 24 with the end surfaces 40 of the cut outs beingsubstantially V-shaped in crosssection, as in shown in FIG. 3.

The two cover members 14 are identical in construction, which simplifiesthe production of this device. One cover member shown in detail in FIGS.5, 6 and 7. Each cover member 14 consists of a main body 50 havingopposite ends 52 and 54 and lateral edges 56 and 58. The end 52 of thecover member has a pair of arms 60a and 60b that are spaced from eachother so that two opposing cover members may be pivoted on asingle pivotaxis with the lateral edges aligned with each other. The two arms, asmore clearly shown in FIGS. and 7, have a substantially common lateraldimension with one of the arms being spaced from its associated lateraledge of the main body by a greater distance than the other arm. In theillustrated embodiment, one of the arms 600 has its outer edge laterallyaligned with the lateral edge 58, while the other arm 60b has its outeredge spaced inwardly from the lateral edge 56 a distance that is atleast equal to the lateral dimension of each of the arms.

The arms positioned as shown, the center line between the pair of armsdoes not coincide with the center line of the cover member so that twocover members may be pivoted with a common pivot axis as shown in FIG.8, with the lateral edges of the two cover members aligned with eachother.

Each arm 60a and 60b has a pivot surface defined thereon which is placedin operative engagement with one of the pins 34 when the cover isassembled on the base. The pivot surfaces each have an arcuate portion62 circumscribing an arc of substantially less than 180 with a flattenedportion 64 on the end thereof, for a purpose that will be describedlater.

The-opposite end 54 of the main body has a latch arm 66 integraltherewith that extends downwardly and has an inwardly directedsubstantially V-shaped groove 68 that corresponds in configuration tothe V-shaped surface 40 defined on the base. The arm 66 is alsolaterally ofiset from the center line of the cover so that the latcharms of the respective cover members are laterally spaced from eachother when the cover members are positioned on opposite sides of thebase. The outer end of the arm has an inclined camming surface 69 toguide the cooperating latch surfaces 40, 68 on the base and the latcharm into engagement with each other.

The main body 50 of the cover member has the general form of a sectionof a sphere between its lateral edges and opposite ends to produce aninner concave surface 70 and an outer convex surface 72 both of whichcorrespond substantially in configuration to the configuration of theconvex surfaces 22 on the base. A plurality of circumferentially spacedslots 74 extend between the surfaces of the cover to allow fluid to passthrough the main body of the cover member.

If desired, the cover members may have suitable indicia so that a usermay identify the appropriate lens for each eye. One type of indicia thatcould be used is to have the center portion of the cover memberflattened with a heart embossed on the flattened portion of the covermember. Since the heart is located on the left side of the body, theuser would identify the lens enclosed by this cover member for the lefteye.

Referring to FIG. 1, it will beseen that the cap 16 has an integralextension that defines a slot 82 which corresponds to thecross-sectional configuration of the extension 30 on the base 12 so thatthe base can be removably secured to the cap. The cap also has athreaded internal surface 84 that may be threaded onto the externalthreaded surface 86 on the upper open end of the container 18 so thatthe cap may be removably coupled to the container.

In assembling the holder, it is necessary to initially place the covermembers on the base before the base is attached to the cap 16. This isaccomplished by positioning the two cover members 14 substantially inthe position shown in FIG. 1 where the flat portions 64 of the pivotsurfaces on the arms 60a and 60b are substan tially aligned with the endsurface 37 on the body 20 of the base. From an inspection of the pivotsurface in FIGS. 6, it will be seen that the cover member must belocated so that the main body of the cover member defines an anglegreater than 90 with respect to the main body 20 of the base. In thisposition, the free end of each arm 60a and 60b is capable of beinginserted into the gap 36 defined between the periphery of each pin 34and the adjacent end surface 37 of the base body.

One arm of each pair of arms of the respective cover members is receivedinto the gap 36 defined between the pin 34 and the end surface 37. Byproperly dimensioning the arms and laterally offsetting the arms 60a and60b relative to the center line of the cover, the cross-sectionaldimension of the two arms received in an associated gap 36 willsubstantially completely fill the gap between the lateral edge 32 of theextension and the lateral edge 24 on the base, as well as the spacebetween the end surface 37 and the pins 39. This dimensioning andpositioning of the arms relative to the end of the cover members willmaintain the lateral edges of the cover members aligned with each otherand with the lateral edges of the base, as is more clearly shown in FIG.8.

Both cover members may then be moved to a closed position (see the lefthand cover member in FIG. 9), so

that each V-shaped groove 68 receives and associates V-shaped surface 40to securely hold the cover members in a closed position, wherein theconvex and concave surfaces on the base and the cover members,respectively, are in juxtaposed relation to each other. It will be seenfrom an inspection of F IG. 8 that one latch arm 66 is received in oneof the cut-outs 38, while the opposite latch arm 66 is received in theopposite cutout 38.

Another feature of the present invention is that the cover memberscannot be removed from the base while the base is secured to the cap.This feature is more clearly shown in FIG. 9, wherein one of the covermembers is shown in its fully opened position when the extension 30 islocated in the slot defined by the extension 80 in the cap 16. In thefully opened position, shown by the right hand cover member 14, the mainbody 50 of the cover defines an angle less than 90 with respect to themain body of the base. In this position, which is termed the maximumpivoted position for the cover members on the base, the flat portions 64of the pivot surfaces are angularly related relative to the end surface37 on the base and terminate close to the centers of the pins so thatthe arms 60 cannot be removed from the gaps 36. This maximum pivotedposition for the cover members is located between the extreme pivotableposition for the cover members, which allows the cover members to beseparated from the base, and the closed position for the cover membersso that there is no way that the cover members can be separated from thebase without removing the base from the cap.

After the cover members, base and cap have been interconnected as shownin FIG. 9, a pair of contact lenses C may be positioned on the convexsurfaces 22 of the base. The cover members or means carried by the basemay then be pivoted to the closed position, wherein the cooperatinglatch surfaces 40 and 68 are in engagement with each other to latch thecover members in a closed position on the base. It will be noted that inthe closed position substantially all of the inner and outer surfaces ofeach contact lens are exposed through the slits 26 and slots 74. g

The container 18 may then be filled with a saline solution in sufficientquantity to immerse the contact lenses. The cap 16 can then be screwedonto the container to completely enclose the container, while thecontact lenses are suspended within the container.

The solution may then be heated by immersing the container in boilingwater for the sterilizing process, and after sterilization the lensesmay remain in the container until they are to be used again.

The entire unit, having a minimum number of parts, can readily bemanufactured from a plastic material at a minimum cost and results in anextremely useful, well constructed device.

What is claimed is:

l. A lens holder comprising a base having first and second correspondingconvex surfaces on opposite sides; means defining a pivot axis on saidbase adjacent said surfaces; first and second cover members of identicalconstruction respectively cooperating with said opposite sides of saidbase, each of said cover members having a concave surface correspondingsubstantially to the configuration of said convex surfaces; a pair ofarms at one end of each cover member defining pivot surfaces to receivesaid pivot axis in operative engagement therewith, said arms beingpositioned sothat said first and second cover members have lateral edgesaligned with each other when said members are operatively engaged withsaid pivot axis; and latch means releasably retaining said cover membersin a closed position on said base with the convex and concave surfacesin juxtaposed relation to each other.

2. A lens holder as defined in claim 1, in which said base has anextension at one end, further including a container and a cap adapted tobe removably coupled with said container, said cap having means forreceiving said extension to secure said base to said cap, said means forreceiving said extension being positioned to locate said base in saidcontainer when said cap is coupled to said container.

3. A lens holder as defined in claim 2, in which said cover members arepivotable to an extreme position to separate said cover members fromsaid base and in which said cap defines a maximum pivoted position forsaid cover members, said maximum pivoted position being located betweensaid extreme position and said closed position to prevent said covermembers from being separated from said base when said base is secured tosaid cap.

4. A lens holder as defined in claim 2, in which said base and cap, whenin assembled condition, are removably secured to each other.

5. A lens holder as defined in claim 2, in which each of said pair ofarms at one end of each cover is displaced to one side so that thecenter line between the arms of the pair does not coincide with thecenter line of the cover and in which said cover members are pivotablyto an extreme position to separate said cover members from said base,said cap defining a maximum pivoted position for said cover members,said maximum pivoted position being located between said extremeposition and said closed position to prevent said cover members frombeing separated from said base when said base is secured to said cap.

6. A lens holder as defined in claim 1, in which each of said pair ofarms at one end of each cover is displaced to one side so that thecenter line of the arms of each pair does not coincide with the centerline of the cover.

7. A lens holder as defined in claim 1, in which said base has slitsextending from the respective convex surfaces. v

8. A lens holder as defined in claim 7, in which each cover member hasslots extending from its concave surface.

9. A lens holder as defined in claim 1, in which said base has lateraledges aligned with the lateral edges of said cover members, furtherincluding an extension at one end of said base, said extension havinglateral edges spaced inwardly from the lateral edges of said base, thelateral edges of said extensions having integral pins extendingoutwardly to define said pivot axis.

10. A lens holder as defined in claim 9, in which said pins arepositioned to define gaps between said base the theperiphery of saidpins and in which one arm of each pair of arms is located in arespective gap, said arms substantially filling said gaps between thelateral edges of said base and said extension.

1 1. A lens holder as defined in claim 10, in which said latch meansincludes a latch arm on the opposite end of each cover member, saidlatch arms being laterally offset from the center line of said covermembers between said lateral edges, said latch arms and the opposite endof said base having cooperating latch surfaces to releasably retain saidcover members in a closed position on said base.

12. A lens holder as defined in claim 1 l, in which said base has slitsextending from the respective convex surfaces and each cover member hasslots extending from its concave surface to an opposed surface.

13. A lens holder as defined in claim 10, in which said pivot surfaceshave cylindrical portions circumscribing an arc of less than 180 so thatsaid cover members are pivotable to an extreme position to separate saidcover members from said base.

14. A lens holder comprising a base having first and secondcorresponding convex surfaces on opposite sides, means defining a pivotaxis on said base adjacent said surfaces, first and second cover membersof identical construction respectively cooperating with said oppositesides of said base, each of said cover members having a concave surfacecorresponding substantially to the configuration of said convexsurfaces, means at one end of each cover member defining pivot surfacesto receive said pivot axis in operative engagement therewith, said meansbeing positioned so that said first and second cover members havelateral edges aligned with each other when said members are operativelyengaged with said pivot axis; and latch means releasably retaining saidcover members in a closed position on said base with the convex andconcave surfaces in juxtaposed relation to each other.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,770,113 Dated November 6, 1973 Inventor(5) Michael D. Thomas It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In the Abstract, delete the underscoring.

Column 2, line 23, change "inventory" to -tooling--.

Column 2, line 35, "prespective" should be -perspective-.

Column 3, line 27, change "the" to --that- (second occurrence) Column 3,line 31, change "in" to --is-- (second occurrence).

Column 3, line 52, "The arms" should be --With the arms.

Column 3, line 61, after "arcuate" add -or cylindrical-.

Column 5, line 1, change "and associates" to --an associated--.

Column 6, lines 31 and 32, "pivotably" should be pivotable- Column 6,line 58, delete "the".

Column 8, after line 14, insert the following claims:

15. A lens holder for supporting a pair of contact lenses comprising abase having a pair of integral convex surfaces defined on opposite sidesthereof for supporting a pair of contact lenses thereon; a cover memberfor each of said pair of convex surfaces, each cover membercorresponding substantially in configuration to the .convex surfaces onsaid base; and means releasably retaining said cover members on saidbase so that the contact lenses are supported between said surfaces.

16. A lens holder as defined in claim 15, in which said base has slitsextending from the respective convex surfaces and each cover member hasslots extending from its concave surface to an opposed surface.

On the cover sheet, "114. Claims" should read 16 Claims Signed andsealed this 25th day of June 197k.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. c. MARSHALL DANN Attestins; Officer Commissionerof Patents FORM PO-1050 (10-69) USCOMM-DC 00376-P69 I u.$. GOVERNMENIPRINTING OFFICE: I969 O--J66-JJI

1. A lens holder comprising a base having first and second correspondingconvex surfaces on opposite sides; means defining a pivot axis on saidbase adjacent said surfaces; first and second cover members of identicalconstruction respectively cooperating with said opposite sides of saidbase, each of said cover members having a concave surface correspondingsubstantially to the configuration of said convex surfaces; a pair ofarms at one end of each cover member defining pivot surfaces to receivesaid pivot axis in operative engagement therewith, said arms beingpositioned so that said first and second cover members have lateraledges aligned with each other when said members are operatively engagedwith said pivot axis; and latch means releasably retaining said covermembers in a closed position on said base with the convex and concavesurfaces in juxtaposed relation to each other.
 2. A lens holder asdefined in claim 1, in which said base has an extension at one end,further including a container and a cap adapted to be removably coupledwith said container, said cap having means for receiving said extensionto secure said base to said cap, said means for receiving said extensionbeing positioned to locate said base in said container when said cap iscoupled to said container.
 3. A lens holder as defined in claim 2, inwhich said cover members are pivotable to an extreme position toseparate said cover members from said base and in which said cap definesa maximum pivoted position for said cover members, said maximum pivotedposition being located between said extreme position and said closedposition to prevEnt said cover members from being separated from saidbase when said base is secured to said cap.
 4. A lens holder as definedin claim 2, in which said base and cap, when in assembled condition, areremovably secured to each other.
 5. A lens holder as defined in claim 2,in which each of said pair of arms at one end of each cover is displacedto one side so that the center line between the arms of the pair doesnot coincide with the center line of the cover and in which said covermembers are pivotably to an extreme position to separate said covermembers from said base, said cap defining a maximum pivoted position forsaid cover members, said maximum pivoted position being located betweensaid extreme position and said closed position to prevent said covermembers from being separated from said base when said base is secured tosaid cap.
 6. A lens holder as defined in claim 1, in which each of saidpair of arms at one end of each cover is displaced to one side so thatthe center line of the arms of each pair does not coincide with thecenter line of the cover.
 7. A lens holder as defined in claim 1, inwhich said base has slits extending from the respective convex surfaces.8. A lens holder as defined in claim 7, in which each cover member hasslots extending from its concave surface.
 9. A lens holder as defined inclaim 1, in which said base has lateral edges aligned with the lateraledges of said cover members, further including an extension at one endof said base, said extension having lateral edges spaced inwardly fromthe lateral edges of said base, the lateral edges of said extensionshaving integral pins extending outwardly to define said pivot axis. 10.A lens holder as defined in claim 9, in which said pins are positionedto define gaps between said base the the periphery of said pins and inwhich one arm of each pair of arms is located in a respective gap, saidarms substantially filling said gaps between the lateral edges of saidbase and said extension.
 11. A lens holder as defined in claim 10, inwhich said latch means includes a latch arm on the opposite end of eachcover member, said latch arms being laterally offset from the centerline of said cover members between said lateral edges, said latch armsand the opposite end of said base having cooperating latch surfaces toreleasably retain said cover members in a closed position on said base.12. A lens holder as defined in claim 11, in which said base has slitsextending from the respective convex surfaces and each cover member hasslots extending from its concave surface to an opposed surface.
 13. Alens holder as defined in claim 10, in which said pivot surfaces havecylindrical portions circumscribing an arc of less than 180* so thatsaid cover members are pivotable to an extreme position to separate saidcover members from said base.
 14. A lens holder comprising a base havingfirst and second corresponding convex surfaces on opposite sides, meansdefining a pivot axis on said base adjacent said surfaces, first andsecond cover members of identical construction respectively cooperatingwith said opposite sides of said base, each of said cover members havinga concave surface corresponding substantially to the configuration ofsaid convex surfaces, means at one end of each cover member definingpivot surfaces to receive said pivot axis in operative engagementtherewith, said means being positioned so that said first and secondcover members have lateral edges aligned with each other when saidmembers are operatively engaged with said pivot axis; and latch meansreleasably retaining said cover members in a closed position on saidbase with the convex and concave surfaces in juxtaposed relation to eachother.